CompactPCI computer systems employ industry standard mechanical components and high performance connector technologies to provide an optimized system intended for rugged applications. A CompactPCI-based computer system is electrically compatible with the peripheral component interconnect (PCI) Specification, allowing low cost PCI components to be utilized in a mechanical form factor suited for rugged environments.
A PCI bus architecture is widely employed in a variety of computer systems, ranging from desktop or notebook personal computers, to industrial-type computer systems, such as network servers. In this regard, industrial and/or embedded computer systems require a more robust mechanical form factor as compared to desktop-type computer systems, due to the harsh environment in which these industrial systems are normally operated, and the high performance application requirements of the industrial systems. To this end, a consortium known as the PCI Industrial Computer Manufactures Group (PICMG®) has promulgated the CompactPCI® Specification that defines industry standard mechanical component and high performance connector technologies for optimized systems intended for rugged applications. The CompactPCI® Specification is described in CompactPCI Specification, by PICMG, 301 Edgewater Place, Suite 500, Wakefield, Mass., and is available at www.picmg.org. PICMG and CompactPCI are registered trademarks of the PCI Industrial Computer Manufacturers Group.
In addition to prescribing a variety of bus and software parameters, the CompactPCI® Specification defines a form factor for boards or cards insertable into and operational with a CompactPCI computer system. A CompactPCI computer system generally includes an outer chassis and a connector plane, such as a backplane board or a mid-plane board, forming various connectors and bus circuitry. The CompactPCI computer system typically includes a number of other components, such as processor cards, input/output (I/O) cards, memory cards, power supply(s), hard disk drive(s), cooling fan(s), etc. The chassis and the connector plane combine to define a series of slots into which PCI cards are inserted. The PCI cards, or more particularly CompactPCI form factor cards, vary widely in terms of configuration and function, ranging from system processor cards to peripheral or I/O cards such as mezzanine cards, digital control cards, relay control cards, and the like.
CompactPCI cards include 3U cards (I 00 mm by 160 mm) and 6U cards (233.35 mm by 160 mm). In addition, the CompactPCI® Specification requires that the maximum spacing between cards, or thickness of a CompactPCI card and its components, is less than 20.32 mm. This 20.32 mm spacing is often referred to as the CompactPCI unit width, and herein defined as unit width spacing. Thus, each slot defined by the chassis and the connector plane is by definition one unit width and the board-to-board distance between CompactPCI cards is less than one unit width.
The CompactPCI® Specification requires that a CompactPCI-based computer system include one or more CompactPCI bus segments. Each CompactPCI bus segment comprises up to eight CompactPCI board locations having the required one unit width board-to-board spacing. Each CompactPCI segment comprises one system slot, and up to seven peripheral slots. Furthermore, bus segments are required to not have more than eight slots without one or more PCI bridges.
The connector plane is oriented parallel with front and back panels, thereby establishing a front region and a back region. In a CompactPCI chassis/connector plane configuration employing a backplane as the connector plane, the front region has a depth of approximately eight inches and the back region has a depth of approximately four inches. The front region of a CompactPCI computer system chassis having a backplane is configured to load and operate the various CompactPCI cards, whereas the back region serves as a transition zone for receiving one or more transition modules related to the CompactPCI card inserted into the corresponding front side slot. In a CompactPCI chassis employing a mid-plane as a connector plane, both the front and back regions of the CompactPCI-based computer system are configured to load and operate the various CompactPCI cards.
In a conventional CompactPCI-based computer system, each card is typically inserted directly into a slot directly connected to the connector plane. As a result, in such a conventional CompactPCI arrangement, each card occupies one of the limited available slots. Furthermore, each connection location at the connector plane is typically protected against electromagnetic interference (EMI). Consequently, each added card typically necessitates additional EMI shielding.
Each CompactPCI card is connected to the connector plane by a set of connector pins. Connection of the CompactPCI card to the connector plane therefore requires a substantial insertion force, and a corresponding substantial extraction force, upon removal. Conventionally, the CompactPCI card is included in a CompactPCI blade assembly. The CompactPCI blade assembly includes an extractor opposite the CompactPCI card connector pins for removing the CompactPCI blade assembly from a CompactPCI-based computer system.
One conventional multi-card, single slot CompactPCI blade assembly comprises a mezzanine card electrically connected to a main printed circuit assembly (PCA) card via a hard shell mated pair connector. This conventional multi-card, single slot CompactPCI blade assembly is inserted into the connector plane via the connector pins on the main PCA. The hard shell mated pair connector allows electrical signal transmission between the mezzanine card and the main PCA card and also allows the main PCA and mezzanine together as an assembly to occupy less than one unit width. The hard shell mated pair connector is not impedance matched, resulting in reduced signal quality. If the mezzanine card were directly connected to the connector plane, it would be spaced 20.32 mm from the main PCA.
Because the conventional multi-card, single slot CompactPCI blade assembly is constrained to fit within one unit width, little room is available between the boards for connecting large components to either board. As a result, the board-to-board spacing is inherently less than one unit width, and cooling the components attached to the cards is limited due to their close spacing.
When servicing a CompactPCI-based computer system, the conventional multi-card, single slot CompactPCI blade assembly is typically removed from the connector plane, electrically de-coupled from the computer system, and then the mezzanine card is typically de-coupled from the main PCA by mechanically separating the two cards. As a result, servicing the cards requires tools and electrically disconnecting the boards. When the mezzanine card is electrically de-coupled from the main PCA, the opportunity to diagnostically read the electrical signal between the cards is lost.
There is a high demand for adding mezzanine cards to a CompactPCI-based computer system in such a way to improve the signal quality between the mezzanine card and the main PCA and to provide more space between the mezzanine card and the main PCA. CompactPCI-based computer systems are required to conform to the CompactPCI® Specification. Even so, the above-described CompactPCI-based computer system design is universally accepted and widely available. This design, however, limits the number of mezzanine cards, and the size of the components on the cards, that are usable with the CompactPCI-based computer system. Therefore, opportunities for improved capabilities and servicing remain. For reasons stated above and for other reasons presented in the Description of the Preferred Embodiment section of the present specification, a need exists for a CompactPCI-based computer system configured to receive and operate improved multi-card CompactPCI blade assemblies.